4 7 hurricanes (earth science)

Extended Vocabulary atmospheric pressure cyclones landfall lull torrential typhoons wall clouds Vocabulary hurricane storm surge tornado tropical depression tropical storm vortex Picture

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Scott Foresman Science 4.7

Nonfi ction Main Idea and Details • Captions

• Labels

• Diagrams

• Glossary

Severe Storms

ISBN 0-328-13879-7

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Scott Foresman Science 4.7

Nonfi ction Main Idea and Details • Captions

• Labels

• Diagrams

• Glossary

Severe Storms

ISBN 0-328-13879-7

ì<(sk$m)=bdihjb< +^-Ä-U-Ä-U

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1 Why are hurricanes such dangerous

weather events?

2 List two factors that must be present

in order for a hurricane to form

3 Explain how a storm surge happens.

meteorologists have ways to monitor storms such as hurricanes Write to describe some of the ways they do this

Use details from the book to support your answer

5 Main Idea and Details Hurricanes

are severe storms What details from the book support this idea?

What did you learn?

Extended Vocabulary

atmospheric pressure cyclones

landfall lull torrential typhoons wall clouds

Vocabulary

hurricane

storm surge

tornado

tropical depression

tropical storm

vortex

Picture Credits

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Opener: The Science Museum/©DK Images;1 ©Bettmann/Corbis; 4 (B, BR) Getty Images; 5 (BR) The Cinema Museum/

Ronald Grant Archive; 6 (TL) ©Bettmann/Corbis, (BL) The Science Museum/©DK Images, (T) Schenectady Museum/

Hall of Electrical History Foundation/Corbis, (CR) Brand X Pictures; 8 (TL) ©Bettmann/Corbis, (B) Science Museum,

London/DK Images; 9 (TR) ©Alfred Pasieka/Photo Researchers, Inc.; 10 (TL) ©Bettmann/Corbis; 11 (CR) Reuters/Corbis;

12 (TL) ©Bettmann/Corbis, (B) Science Source/Photo Researchers, Inc.; 14 (TL) Hulton-Deutsch Collection/Corbis.

ISBN: 0-328-13879-7

This publication is protected by Copyright, and permission should be obtained from the publisher prior to any

prohibited reproduction, storage in a retrieval system, or transmission in any form by any means, electronic,

mechanical, photocopying, recording, or likewise For information regarding permission(s), write to

Permissions Department, Scott Foresman, 1900 East Lake Avenue, Glenview, Illinois 60025.

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by Peggy Bresnick Kendler

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A hurricane is a dangerous storm with very strong

winds A hurricane is made up of many groups of

thunderstorms that are wrapped around its center

Tropical storms form from heat and water vapor

from the ocean Warm, moist air rises, causing a tropical

disturbance The clouds in a tropical disturbance can

become thunderstorms The storms’ winds increase

and begin to swirl, causing a tropical depression Winds

blow faster and form a tropical storm When winds

reach a speed of 119 kilometers per hour, the tropical

storm becomes a hurricane The center of a hurricane is

called the eye Winds are calm in the eye

A hurricane can knock down trees or change the

shape of a coastline A slow-moving hurricane can

produce many inches of rain in one place This can

cause dangerous mudslides and fl oods A hurricane’s

winds can push large waves of ocean water onto the

shore This rise in sea level is called a storm surge

Computer models can predict a hurricane’s strength,

direction, and speed Satellites can send data on

storms and hurricanes to meteorologists Many

scientists work together to forecast storms

What You Already Know

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A funnel cloud is a rapidly spinning column

of air that drops down out of a thunderstorm

It is called a tornado when it touches the ground

A tornado forms from a spinning area inside a thunderstorm A vortex is an area where air or liquid spins in circles

A tornado is a vortex that forms in

a thunderstorm

Tornadoes form and move quickly They are diffi cult

to forecast Their strong winds can cause a great deal of damage

Hurricanes and tornadoes are both strong storms Tornadoes have faster winds than hurricanes have Hurricanes are bigger than tornadoes, and they last longer Keep reading to learn more about hurricanes

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What are hurricanes?

Hurricanes are very large

tropical storms that form

over warm water Hurricanes,

typhoons, and cyclones are all

different names for the same

type of storm In the western

Pacifi c Ocean, hurricanes are

called typhoons In the Indian

Ocean, they are called cyclones

In the Atlantic Ocean, they are

called hurricanes

Hurricanes have winds that have reached a

constant speed of at least 119 kilometers per hour

These winds blow in a spiral pattern around a calm

center area called the eye

satellite image of a hurricane

The strong winds of a hurricane

can knock over trees.

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The eye of a hurricane

is usually between twenty and one hundred kilometers wide The storm can bring heavy rains, powerful winds, and storm surges A single hurricane can spend more than two weeks over open water

Hurricane season in the Atlantic Ocean north of the equator lasts from June 1 through November 30 During these months, the water in the Atlantic Ocean is warmest

Most hurricanes happen in August and September

All tropical storms are given male

or female names

The names help meteorologists identify and track storms—especially when more than one happens at the same time.

Storm Names

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How Hurricanes Form

Hurricanes start as small thunderstorms over warm,

tropical oceans They begin over a warm layer of water

at the top of the sea This layer has a surface temperature

of at least 26.5˚ Celsius, or 80˚ Fahrenheit The warm

seawater is absorbed by the air This moist, warm air

affects the atmospheric pressure Atmospheric pressure

is the pressure caused by the

weight of air

October 22, 1998: A storm

begins to form over the

Atlantic Ocean.

October 25, 1998: As the storm develops into a hurricane, the eye becomes visible.

Hurricane Mitch 1998

The map shows the places

where severe storms are

most likely.

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Most hurricanes in North America happen when different water currents meet When these currents come together, they produce a group of thunderstorms called a tropical disturbance The disturbance grows as warm, moist air moves upward As the air rises, it cools and the water in it condenses and releases heat This causes lower atmospheric pressure, which pulls even more air into the system

As the wind moves faster, the tropical disturbance becomes a tropical depression As air moves into it, the system begins to spin around When the storm’s winds grow to 62 kilometers per hour or greater, it becomes a tropical storm, and it is given a name If the storm keeps growing and its wind speeds reach 119 kilometers per hour, it is a hurricane

October 26, 1998: Hurricane Mitch becomes larger and more powerful.

October 28, 1998: After it reaches land, Hurricane Mitch loses strength.

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Inside a Hurricane

At Earth’s surface, the air pressure in a

hurricane is low When the air moves from areas

of high pressure to areas of low pressure, strong

winds develop The warm, moist air from the

ocean moves to areas of low pressure There the

air rises and forms bands of rain These rain

bands can produce more than fi ve centimeters of

rain per hour

The powerful winds of a hurricane swirl

around the eye of the storm A hurricane’s

eye is calm Within the eye, there are few

winds or clouds

around eyewall

spiraling bands

of wind and rain

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Storm clouds called wall clouds surround the eye to form the eyewall A hurricane’s strongest winds and heaviest rains happen within wall clouds that spin around the eye In the eyewall, warm air spirals upward, causing the most powerful winds of the storm

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Storm Damage

When a hurricane strikes land, we say it has made

landfall As the hurricane moves over land, powerful

winds and heavy rains can remain over an area for several

hours Its raging winds can reach a speed of more than

250 kilometers per hour The winds and rains can do

tremendous damage Hurricane winds can rip trees out

of the ground, tear the roofs off buildings, and shatter

windows The torrential rains can cause heavy fl ooding

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As the hurricane’s eye passes over an area, the winds slow and the sky might clear There is a lull, or

a brief calm, in the storm When the lull passes, the intense winds and heavy rains resume This is because the most powerful winds of the storm surround the hurricane’s eye

Hurricanes weaken as they move over land They need energy from the warm sea air to stay powerful

This destruction was caused by Hurricane Frances, which battered Florida in 2004.

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Storm Surge

A hurricane can cause storm surges A storm surge

occurs when the hurricane pushes ocean water onto

the shore During a hurricane, ocean water is pulled up

into the eye This makes enormous waves that gain even

more power from the strong hurricane winds The result

is a wall of seawater that crashes onto land

Some of the worst damage from a hurricane is

caused by storm surges They are especially dangerous

in areas where the coast is at almost the same level as

the ocean During a storm surge, ocean water pours

onto land with tremendous force, fl ooding streets

and buildings Buildings on hills are not as likely to

fl ood, but they are sometimes damaged by

mudslides that result from the heavy rain

Storm surges form when

ocean water is pulled into

the hurricane’s eye.

When Hurricane Frances struck Florida in 2004, some boats were washed inland

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Besides fl ooding coastal areas, storm surges can do plenty of damage to property Rapid rises in sea level can damage or destroy portions of bridges Storm surges also can lift large boats, wrecking

them as they wash up on the shore or even onto roads

Storm surges can also be very dangerous for animals and people who

get caught in the rushing water

Waves pounded the island

of Bermuda as a hurricane struck in 2003.

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Monitoring Storms

Predicting and tracking hurricanes are important

jobs of weather forecasters and meteorologists They

alert people to the growing storm People in areas

where the hurricane might strike have time to prepare

for the storm

Weather forecasters use images from satellites

to help them follow a hurricane’s development over

the ocean The images help them track a hurricane’s

progress and its path This way, the forecasters can have

a good idea where the storm will make landfall

The National Oceanic and Atmospheric

Administration, known as NOAA, sends specially

equipped planes to fl y right into the center of

hurricanes The planes carry meteorological equipment

that gathers data inside the storms The data are fed

into computer models that help forecasters make

accurate predictions during a hurricane Data also help

researchers better understand what goes on inside

storms and hurricanes

This information helps meteorologists

to be better hurricane forecasters

Meteorologists study satellite images to help them understand and predict hurricanes

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Devices on the weather-research planes measure air pressure, humidity, temperature, and wind direction and speed This gives scientists a good idea of the structure and intensity of the storm

Hurricanes are very powerful storms They can cause great damage when they reach land Their strong winds and heavy rains can destroy anything in their path Scientists study hurricanes so they can learn as much as possible about these dangerous storms

A weather-research plane fl ies into the eye of a hurricane to gather information and monitor the storm.

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atmospheric the pressure caused by the weight

of the atmosphere

cyclones hurricanes that form in the

Indian Ocean

landfall the act of a hurricane reaching land

lull a brief calm

torrential fl owing rapidly

typhoons hurricanes that form in the western

Pacifi c Ocean

wall clouds the storm clouds that surround a

hurricane’s eye

pressure

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